The present invention relates to polymeric cutout assemblies for power distribution systems. More particularly, the present invention relates to an insulator assembly for a polymeric cutout assembly. Still more particularly, the present invention relates to anti-rotational end caps, sleeve and center pin assemblies, and non-ceramic insulation for insulator assemblies.
A cutout assembly or sectionalizer is a protective device having a fuse element located between the high voltage power line and the distribution network grid. In the event of a fault due to a high current surge on the power line, the fuse element is designed to blow (melt) and instantly remove power from the section of the grid being protected by the cutout. This device keeps the entire grid from going down; thus, power is lost only in the section where the fault occurred.
A cutout assembly is formed of two basic parts, a fuse link holder built around an insulator and a fuse assembly connected to the fuse link holder. The fuse assembly pivots downward after a fault current activates and blows the fuse element located within the fuse assembly. When the fuse element activates and the fuse assembly pivots downward, considerable physical force is exerted on the insulator. Hence, the insulator is typically made from porcelain or other ceramic materials for added strength to prevent damage when the fuse element activates. These porcelain insulators, however, are usually heavy and bulky, require specialized assembly fixtures or processes, and are awkward to handle and ship. The porcelain insulators, being ceramic, are also brittle and easily chipped or broken. Furthermore, center pins and end pins are attached to the porcelain with a sulfur cement, which adds weight to the assembly and is prone to cracking over time.
When the fuse element of a fuse assembly activates, a lineman from a utility company needs only to see which cutout assembly has a fuse assembly hanging in the downward position. From this he can determine which part of the network grid is faulted, locate and fix the cause of the fault, remove the fuse assembly with a hot stick, replace the fuse element inside the fuse assembly, and reinstall the fuse assembly to reenergize the cutout assembly and once again protect the distribution network grid.
Examples of existing cutout assemblies are disclosed in U.S. Pat. No. 5,300,912 to Tillery et al.; U.S. Pat. No. 5,559,488 to Hassler et al.; U.S. Pat. No. 4,870,387 to Harmon; U.S. Pat. No. 3,594,676 to Misare; and U.S. Pat. No. 2,961,518 to Hermann.
Center pins and end pins are often attached to porcelain with a sulfur cement, which results in a heavy and bulky insulator assembly. That increases the required inventory for the cutout assembly and increases assembly and handling time. Thus, there is a continuing need to provide improved insulator assemblies for polymeric cutout assemblies for power distribution systems.
Accordingly, it is an object of the present invention to provide an insulator assembly for a polymeric cutout assembly that has a center tube and end caps that are connected to the rod without the use of a sulfur cement.
Another object of the present invention is to provide an insulator assembly to which the center tube and end caps are crimped to the rod, an insulator is molded around the rod assembly, and a center pin is crimped to the center tube.
The foregoing objects are basically attained by an insulator assembly for a polymeric cutout assembly. The insulator assembly has a core that has first and second ends and an outer surface. First and second end caps are attached at the first and second core ends, respectively. The end caps have outer surfaces. A sleeve is disposed on the outer surface of the core. A projection extends laterally outwardly from an outer surface of the sleeve. An insulator is molded around the outer surface of the core, the sleeve and the first and second end caps. A center pin is attached to the projection. By forming the insulator assembly in this manner, a cutout assembly is assembled that is not brittle and prone to cracking over time, thereby providing a cutout assembly having a longer useful lifetime. Furthermore, the cutout assembly requires fewer parts to assembly, thereby reducing inventory and resulting in a lighter and easier to assemble cutout assembly.
Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the invention.